"We’re here again. A powerful and determined president is squaring off against an independent investigator operating inside the Justice Department," Woodward and Bernstein wrote in The Washington Post, saying the situations have become "eerily similar."

Trump reportedly only backed off trying to fire Mueller when the White House counsel threatened to resign.

President Nixon demanded the firing of Archibald Cox, the special counsel appointed by Attorney General Elliot Richardson, for his efforts to obtain Oval Office tapes despite Nixon's refusal.

Both Richardson and the deputy attorney general resigned over Nixon's demands, in what became known as the "Saturday Night Massacre."

Woodward and Bernstein said that the Russia story will go on, but that Trump's mistakes have mirrored Nixon's more than once.

"Soon thereafter, Nixon made two fateful miscalculations," they wrote. "He appointed another special prosecutor to replace Cox, and he turned over an initial batch of tapes, including one that vividly incriminated him. The Trump-Mueller history is yet to be written."

Some Republicans in Congress have pushed for the appointment of a second special counsel to investigate possible political bias on Mueller's team. Republicans are now claiming that a surveillance warrant used against a Trump campaign adviser proves political bias in the FBI and an effort by law enforcement to undermine the presidency.

Democrats say the GOP is trying to undermine Mueller's probe, which has already yielded two guilty pleas from former Trump aides, as well as the indictments of two others.

Multiple lawmaker have said the ouster of Mueller would represent a "red line" for Trump.